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AXPZ20 KNHC 182128
TWDEP

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
2128 UTC Sat Nov 18 2017

Tropical Weather Discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis.

Based on 1800 UTC surface analysis and satellite imagery through 2100 UTC.


...SPECIAL FEATURE...

Gulf of Tehuantepec Gale Warning: A brief lull in northerly flow currently in place will be replaced by fresh to near gale force winds by sunrise Sunday, then will increase to gale force by early Sunday afternoon. Winds will further increase to strong gale Sunday night, then will diminish below gale force by Monday afternoon. Seas will build to 15 to 17 ft during the strongest winds and will spread out away from the source region. Looking ahead, fresh to strong drainage flow will then persist through Tuesday morning, with more tranquil marine conditions Tuesday afternoon through Tuesday night. Another northerly gale force wind event is possible Wednesday through the end of the upcoming week.

INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

The monsoon trough extends from 09N78W to 09N94W to 09N105W. ITCZ extends from 09N105W to 10N120W to 10N140W. Scattered moderate and isolated strong convection is within an area bounded by 12N121W to 12N114W to 08N117W to 11N121W, and also within an area bounded by 14N137W to 14N133W to 10N122W to 06N126W to 10N137W to 14N137W. Scattered moderate convection is within an area bounded by 22N140W to 22N135W to 15N136W to 15N140W to 22N140W.


...DISCUSSION...

OFFSHORE WATERS WITHIN 250 NM OF MEXICO...

See the Special Features section for information about the Gulf of Tehuantepec Gale Warning.

A NW to SE oriented ridge just beyond 250 nm seaward will maintain moderate to locally fresh NW flow W of Baja Peninsula through sunrise on Sunday when the pressure gradient will relax, supporting moderate NW flow through sunrise on Monday. Light N winds are then expected through sunrise on Thursday.

Gulf of California: A recent scatterometer pass indicated fresh to near gale force NW to N winds N of 29.5N where a tight pressure gradient is place. Fresh to strong winds will spread southward to 25N by late tonight and seas will build to around 8 ft in the central Gulf. Winds will diminish to 20 kt or less by late Sunday night as the pressure gradient relaxes. Moderate northerly flow is anticipated across the entire Gulf waters by Sunrise on Monday, becoming light Monday night.

OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR...

Gulf of Papagayo: Moderate to locally fresh NE drainage winds are forecast during the overnight hours through the middle of the upcoming week with seas building to 5 to 6 ft downstream near 10N87W.

Light and variable winds, and 3 to 5 ft seas are expected elsewhere to the N of 09N, while moderate to locally fresh southerly winds and 4 to 7 ft seas, are forecast S of 09N through the middle of the upcoming week.

REMAINDER OF THE AREA...

A NE to SW aligned ridge builds from 32N124W to beyond 20N140W. Fresh to locally strong southerly flow will develop across the NW corner of the discussion waters tonight as the pressure gradient tightens between the ridging and a cold front W of the area. Seas will gradually build to 8 to 10 ft by early Sunday afternoon. These winds will continue through Sunday possibly approaching near gale force near 30N140W with seas building to up to 12 ft. The fresh to strong winds will then finally diminish by the middle of the upcoming week. The ridging will hold strong helping to keep the front W of the area with it likely stalling and eventually dissipating W of 140W.

Elsewhere, an area of fresh trades is supporting 8 to 9 ft in mixed swell from 13N to 18N between 129W and 137W. These trades should relax somewhat by early Sunday afternoon allowing for the seas to decay to less than 8 ft.

$$ Lewitsky

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